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Biomedical subjects

A R Subramanian

Publications and source records attributed to A R Subramanian.

At least 55 records · Page 3Linked to original sources
PubMed1989

The polymorphic human chaperonin protein HuCha60 is a mitochondrial protein sensitive to heat shock and cell transformation.

The HuCha60 protein, a polymorphic protein on two-dimensional gels of human lymphocytes, is found to be structurally and functionally related to the Escherichia coli groEL gene product: The structural homology is evident from the N-terminal amino-acid sequence analysis and from the immunological cross-reactivity with an antiserum against the E. coli groEL gene product. The functional homology is suggested by the heat sensitivity and the growth dependence of this protein. Both genetic variants of the HuCha60 occurring on the two-dimensional protein pattern of lymphocytes, the common "a" variant and the rare "b" variant, are strongly enhanced after heat shock. The expression of the HuCha60 in resting or normally growing cultures human cells is in general low, whereas in mitogen-stimulated cells or transformed cell lines the synthesis of the HuCha60 is strongly enhanced. After cell fractionation and subsequent two-dimensional gel electrophoresis and immunoblotting, the HuCha60 has been found to be mainly expressed in mitochondria. In the cytosol fraction two different molecular weight forms of the HuCha60 have been observed with low expression. Also in the nuclear fraction, HuCha60 is present in low concentration.

Cell Division↗
PubMed1988

Nucleotide sequence and linkage map position of the genes for ribosomal proteins L14 and S8 in the maize chloroplast genome.

The nucleotide sequence of a 1287-base-pair segment of the maize (Zea mays) chloroplast DNA, encoding chloroplast ribosomal proteins L14, S8 and the C-terminal part of L16, has been determined using the dideoxy-chain-termination method. These data from a monocot plant are compared to the corresponding data from a dicot and a lower plant and from two bacteria. The deduced amino acid sequence of maize chloroplast L14 shows 80%, 81%, 51% and 52% and that of S8 shows 75%, 58%, 39% and 38% sequence identity, respectively, to the corresponding sequences of Nicotiana tabacum, Marchantia polymorpha, Bacillus stearothermophilus and Escherichia coli. The starting map coordinates of rpL14 and rpS8 in the physical map of the maize chloroplast DNA [Larrinua, I. M., Muskavitch, K. M. T., Gubbins, E. J. and Bogorad, L. (1983) Plant Mol. Biol. 2, 129-140] are 31.330 and 31.841. The gene order is rpL16-spacer-rpL14-spacer-rpS8. Shine-Dalgarno sequences (GGA and AGGAGG) and computer-derived stem-loop structures of dyad symmetry are present in the spacers and the 3' downstream region of rpS8, respectively, but a chloroplast promoter-like sequence could not be detected suggesting that the latter might be located further upstream in this ribosomal protein gene cluster in maize chloroplast DNA.

Amino Acid Sequence↗
PubMed1988

Nucleotide sequence of maize chloroplast rpS11 with conserved amino acid sequence between eukaryotes, bacteria and plastids.

Nucleotide sequence of a 721 base pair segment of maize chloroplast DNA, encoding the putative chloroplast ribosomal protein S11 at physical map position 33.1-33.5 Kbp, is described. A Shine-Dalgarno sequence and computer-derived stem-loop structures of dyad symmetry are present in the spacer region between rpS11 and its 5' upstream gene rpL36. The deduced amino acid sequence of maize chloroplast S11 shows 69%, 66%, 62%, 57%, 48% and 45% sequence identity to the corresponding sequences of tobacco, spinach, pea, liverwort, Escherichia coli and Bacillus subtilis, respectively, and 41% sequence identity to three eukaryotic cytoplasmic ribosomal proteins, S14 of Chinese hamster and of human and rp59 of yeast. Maize chloroplast r-protein S11 is larger than the other published S11s of plants and bacteria, due to the apparent tandem introduction of a short sequence stretch of internal homology.

Amino Acid Sequence↗
PubMed1987

Nucleotide sequence, promoter analysis, and linkage mapping of the unusually organized operon encoding ribosomal proteins S7 and S12 in maize chloroplast.

The nucleotide sequence of the operon encoding maize chloroplast ribosomal protein genes S7 and S12 and the promoter activity of a chimeric construct of the -10/-35 sequence of this operon (attached to a promoterless chloramphenicol acetyltransferase gene) have been determined. This operon occurs in the chloroplast genome divided in two parts: part A contains exon 1 of rpS12 (encoding the N-terminal 38 amino acid residues), whereas part B has the following structure: promoter-rpS12 (exon 2 + intron + exon 3)-spacer-rpS7-terminator. Part A is located at the approximate coordinate position 41000, whereas two copies of part B are located at two distant locations in the genome at coordinate positions 18700 and 120200. This unusual organization of the S12 operon in maize (a monocot plant) is similar to that reported in a dicot and a lower plant. The deduced amino acid sequence of maize chloroplast S7 shows 43, 38, 71, and 85% and of S12 shows 66, 72, 91 and 90% sequence identity to the corresponding sequences of Escherichia coli, Euglena gracilis, Marchantia polymorpha, and Nicotiana tabacum, respectively. The promoter upstream of rpS12 (part B) is transcriptionally active in E. coli.

Amino Acid Sequence↗
PubMed1987

Nucleotide sequence and linkage map position of the secX gene in maize chloroplast and evidence that it encodes a protein belonging to the 50S ribosomal subunit.

The nucleotide sequence of the segment of maize chloroplast DNA lying between the map coordinate positions 32.59 and 32.98 Kb and containing the secX gene has been determined. The derived amino acid sequence of maize chloroplast secX is 95%, 87% and 62% identical to the corresponding derived amino acid sequences from two plant chloroplasts and Escherichia coli, respectively. It is also 70% identical to the experimentally determined amino acid sequence of a protein isolated from Bacillus stearothermophilus ribosomes. Separation of the 50S ribosomal subunit proteins of E. coli by reversed phase HPLC gave a peak which contained pure secX protein, as determined by N-terminal amino acid sequencing. Spinach chloroplast 50S subunit proteins separated by HPLC also gave a peak corresponding to pure secX protein. From these results we conclude that the secX gene in E. coli and in plant chloroplasts encodes a small (37-38 amino acid residues) ribosomal protein belonging to the 50S subunit. The same conclusion has been reached recently by A. Wada with respect to E. coli secX. In agreement with Wada, we name the secX protein L36. Its chloroplast gene is designated rpL36.

Base Sequence↗
PubMed1986

Vivax and falciparum malaria seen at an Indian service hospital.

The cases of 740 adult males with vivax and/or falciparum malaria managed in a military hospital in north-eastern India during the period from June 1978 to March 1981 were analysed. Four hundred and nine (55.3%) were infected with Plasmodium falciparum, 237 (32.0%) with P. vivax and the remaining 94 (12.7%) with both P. vivax and P. falciparum. The majority of cases were chloroquine sensitive and did not pose diagnostic or therapeutic problems. Of 381 patients subjected to an extended field test, 82 (21.5%) exhibited a variable degree of chloroquine resistance. Cerebral and haemopoietic involvement were the commonest of the pernicious syndromes observed in 92 (12.4%) patients. Atypical presentations, variable chloroquine resistance and presentation with complications call for timely recognition and institution of a specific supportive therapeutic regime.

Adolescent↗
PubMed1984

Reconstitution of 50 S ribosomal subunits from Bacillus stearothermophilus with 5 S RNA from spinach chloroplasts and low-Mr RNA from mitochondria of Locusta migratoria and bovine liver.

Reconstitution experiments with 50 S ribosomal subunits from Bacillus stearothermophilus demonstrate that spinach chloroplast 5 S rRNA can be incorporated into the bacterial ribosome and yield biologically active particles, thereby establishing the eubacterial nature of chloroplast 5 S rRNA. In contrast, mitochondria from Locusta migratoria or bovine liver do not appear to contain discrete, low-Mr RNAs, which can replace 5 S rRNA in the functional reconstitution of B. stearothermophilus ribosomes.

Animals↗
PubMed1984

Function of the repeating homologous sequences in nucleic acid binding domain of ribosomal protein S1.

Ribosomal protein S1 contains in its RNA binding domain four repeating, homologous stretches of sequences. Its functionally active mutant form m1-S1 [Subramanian, A.R., & Mizushima, S. (1979) J. Biol. Chem. 254, 4309] contains only three repeating stretches. In order to assess the functional importance of this repeating sequence, we cleaved S1 at its reactive SH group on Cys-349 and isolated a fragment (S1-F4) that has lost two of the homologous stretches but retains all other essential elements. We find that ribosomes reconstituted with S1-F4 instead of S1 are functionally active in translating poly(U) and poly(A) but totally inactive in translating phage MS2 RNA. The significance of this result is discussed vis-à-vis the initiation step in translating natural mRNA, and a functional role for the tetrarepeat of S1 is suggested.

Amino Acid Sequence↗
PubMed1984

Relaxation time, interthiol distance, and mechanism of action of ribosomal protein S1.

The two sulfhydryl groups of ribosomal protein S1 from Escherichia coli have been labeled with fluorescent maleimides and the distance between them has been determined by nonradiative energy transfer. This distance was found to be approximately 27 A for both free S1 and S1 bound to 30 S subunits. This value probably represents an upper limit. The position of the fluorescence emission maximum indicates that both sulfhydryl groups are in a relatively hydrophobic environment. When poly(U) is added to labeled S1, either free or in 30 S subunits, the emission maximum shifts to the red by about 3 nm but without a detectable change in the interthiol distance. S1 labeled at one or both of its sulfhydryl groups retains most of its ability to enhance poly(U)-directed polyphenylalanine synthesis. About the same concentration of poly(U) is required to give the maximum shift in fluorescence as is required to give maximum polyphenylalanine synthesis, indicating that S1 binds poly(U) during translation. The peptide initiation inhibitor aurintricarboxylic acid almost completely quenches the fluorescence from either labeled sulfhydryl groups in S1 bound to ribosomes or free in solution. This quenching probably is due to energy transfer from the labeled sulfhydryls to bound aurintricarboxylic acid. Fluorescence anisotropy measurements indicated that the C-terminal domain of S1 is relatively rigid, but retains some independent movement when attached to ribosomes. The overall data are consistent with a model in which a region near the two sulfhydryl groups in the elongated C-terminal domain functions to sequester and bind mRNA to the ribosome during peptide synthesis.

Anti-Bacterial Agents↗
PubMed1984

Computed spatial homology between the L12 protein of chloroplast ribosome and 1.7 A structure of Escherichia coli L12 domain.

A computer-graphic model of the tertiary structure of a functional domain in an organelle ribosomal protein was generated using the amino acid sequence of chloroplast ribosomal protein L12 from spinach (Bartsch, Kimura and Subramanian, Proc. Natl. Acad. Sci. USA 79, 6871-6875, 1982) and 1.7 A resolution coordinates of the E. coli L12 C-terminal fragment crystal (Leijonmarck, Eriksson and Liljas, Nature 286, 824-826, 1980). A comparison between the model and the experimentally derived structure shows that although 40% of the primary structure of this part of the two proteins has undergone amino acid replacements, the gross spatial structure of the domain is maintained and the character of the surfaces of possible functional importance are not significantly altered.

Amino Acid Sequence↗
PubMed1983

The activity of discrete fragments of ribosomal protein S1 in Q beta replicase function.

As a subunit of bacteriophage Q beta replicase, ribosomal protein S1 is required for tight binding of the enzyme to Q beta RNA and for the initiation of Q beta RNA transcription. To compare these properties of S1 with its functions in protein synthesis, we have reconstituted altered replicase enzymes by adding discrete fragments of S1 to Q beta replicase lacking S1 (R(-S1]. We show that the NH2-terminal region of S1 is required for S1 subunit interactions in replicase since a trypsin-resistant fragment (denoted S1-F1) lacking the NH2-terminal 31% of S1 is functionally inactive and does not seem to bind to R(-S1). Previous studies with S1-F1 indicated that this NH2-terminal region is required for S1 to bind to the ribosome. Our results also show that the COOH-terminal region of S1 is dispensable for S1's function in replicase because a mutant of S1 (m1-S1) lacking 21% of the COOH-terminal portion of the chain is as active as wild type S1 in replicase and binds to R(-S1) with comparable affinity. In protein synthesis, the mutant m1-S1 is known to substitute for S1 but is only about 75% as efficient as wild type S1.

Escherichia coli↗
PubMed1983

Maize chloroplast DNA encodes a protein sequence homologous to the bacterial ribosome assembly protein S4.

A cloned restriction fragment of maize chloroplast DNA (Bam H1 fragment 5) is shown to contain an open reading frame which encodes a basic protein of 201 amino acid residues with 40-50% sequence homology to E. coli ribosomal protein S4. Based on the experimentally determined sequence homology between the highly conserved bacterial ribosomal protein L12 and its chloroplast homologue (Bartsch M., Kimura, M. and Subramanian, A.R. (1982) Proc. Natl. Acad. Sci. USA 79, 6871), we conclude that this reading frame represents the maize chloroplast S4 gene. The nucleotide sequence of a 1100 base pair DNA segment containing the putative gene is presented.

Amino Acid Sequence↗